So an alternate highway makes sense, but why 85 mph? Clearly drivers want to get where they’re going faster, and at 85 mph, the new toll road potentially cuts the drive time from Austin to San Antonio in half.

The Texas Department of Transportation says although it’s fast, the new speed limit is safe. The road was designed for it. It’s straight and through rural areas. But critics point out the Transportation Department had a financial incentive to set the speed higher.

As part of its contract with SH130 Concession Co., the company funding the new toll road, the state would receive $67 million for setting the speed limit at 80 mph and $100 million if the speed was 85 mph. Even so, Chris Lippincott, a spokesman for the company, said, “Drivers retain the ultimate responsibility for safety.”

The new stretch will be from Mustang Ridge, about 10 miles south of Austin’s international airport, to Interstate 10 just east of Seguin. A 50-mile stretch bypassing Austin already is open.

Tolls for personal vehicles displaying an electronic toll tag will be about 15 cents per mile. But no tolls will be collected until Nov. 11.